If you really wantto do this via code and not a prebuilt module, here it is (assuming date format is 'mmm dd yyyy hh:mm(am|pm)' that is 'Feb 19 2001 3:42pm').

use strict;
my $str = "2-19-01 3:49pm";
my %months = qw(1 Jan
            2 Feb
            3 Mar);
my ($month,$day,$year,$time) = split /-|\s/,$str;
my $dataDate = "$months{$month} $day 20$year $time\n";
print $dataDate;
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Jeremy